首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   14546篇
  免费   872篇
  国内免费   54篇
耳鼻咽喉   110篇
儿科学   274篇
妇产科学   178篇
基础医学   2139篇
口腔科学   306篇
临床医学   1478篇
内科学   2523篇
皮肤病学   230篇
神经病学   1954篇
特种医学   1164篇
外科学   2126篇
综合类   98篇
一般理论   4篇
预防医学   576篇
眼科学   335篇
药学   1007篇
中国医学   28篇
肿瘤学   942篇
  2023年   53篇
  2022年   112篇
  2021年   200篇
  2020年   145篇
  2019年   193篇
  2018年   237篇
  2017年   196篇
  2016年   271篇
  2015年   343篇
  2014年   399篇
  2013年   493篇
  2012年   794篇
  2011年   831篇
  2010年   531篇
  2009年   548篇
  2008年   862篇
  2007年   923篇
  2006年   921篇
  2005年   967篇
  2004年   854篇
  2003年   871篇
  2002年   833篇
  2001年   336篇
  2000年   291篇
  1999年   275篇
  1998年   167篇
  1997年   132篇
  1996年   138篇
  1995年   138篇
  1994年   121篇
  1993年   107篇
  1992年   141篇
  1991年   145篇
  1990年   137篇
  1989年   134篇
  1988年   118篇
  1987年   123篇
  1986年   105篇
  1985年   134篇
  1984年   103篇
  1983年   92篇
  1982年   66篇
  1981年   66篇
  1980年   50篇
  1979年   99篇
  1978年   65篇
  1977年   68篇
  1976年   57篇
  1974年   62篇
  1973年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Effect of depressive symptoms on survival after heart transplantation   总被引:3,自引:0,他引:3  
OBJECTIVE: This study explored the value of preoperative self-reported assessment for depression and anxiety in patients who had undergone heart transplantation (HTx). The initial sample was divided into subgroups of patients with ischemic (ICMP) and dilated cardiomyopathy (DCMP). Patient depression and anxiety scores were measured in both subgroups and their impact on pre- and postoperative mortality investigated. METHOD: An initial sample of 152 patients with either ICMP (N = 57) or DCMP (N = 95) and end-stage heart disease awaiting heart transplantation were assessed in a multidimensional longitudinal study, including psychological and somatic variables. One hundred and three patients received a HTx and were followed up for a mean of 4.4 years. Proportional hazard models were computed to test for the influence of psychosocial and somatic factors on outcome. RESULTS: Preoperative depression and state anxiety scores were significantly higher in the ICMP group. In addition to donor and recipient age, ICMP patients in the preoperative high depression group also showed a significantly higher mortality after HTx. This result remained significant even after controlling for sociodemographic and somatic variables. CONCLUSIONS: Patient self-reported depression, but not anxiety, can contribute to the identification of subgroups of patients with an unfavorable outcome after HTx. It therefore may be helpful to screen for depression, particularly in patients with an ischemic cause of their end-stage heart disease. Specific intervention programs should be further developed and evaluated.  相似文献   
92.
Zusammenfassung Aus eigener Zucht stammende Larven, Nymphen und Imagines von Amblyomma testudinis wurden auf ihre Sinnesleistungen hinsichtlich Phototaxis, Thermotaxis, Geotaxis und Chemotaxis untersucht. Es ergab sich ein entwicklungsabhängiger Wandel im phototaktischen Verhalten von anfangs positiver Phototaxis bei den Larven über indifferente Phototaxis bei vollgesogenen Larven und nüchternen Nymphen zu negativer Phototaxis bei vollgesogenen Nympen sowie - und -Imagines. Sämtliche Entwicklungsstadien mit Ausnahme der -Imagines verhalten sich temperaturindifferent vor dem Kontakt mit einem Wirt; vollgesogene Larven und Nymphen dagegen bevorzugen niedrige Temperaturen. Nymphen und Imagines, die noch nicht gesogen haben, reagieren negativ geotaktisch. Sie erklettern vermutlich in der Natur die Spitzen von Pflanzen und Steinen, um dort das Vorbeikriechen eines Wirtes abzuwarten. Imagines von Amblyomma testudinis reagieren mit einer positiven Chemotaxis auf Schlangen stärker als auf Kröten. Auch Substrat aus Schlangenbehältern enthält mindestens für 30 Std nach der Entfernung der Schlangen chemotaktisch wirksame Stoffe.
Contributions to sensory physiology of the tick Amblyomma testudinis
Summary Phototaxis, thermotaxis, geotaxis and chemotaxis of larvae, nymphs and adults of Amblyomma testudinis from own breedings were studied. The phototactic behaviour changed according to the different stages of development: unfed larvae were positively phototactic, fed larvae and unfed nymphs were indifferent, fed nymphs but also the adults showed a negative phototaxis.—All stages of development besides the females reacted without any preference for a distinct temperature, whereas larvae and nymphs after feeding prefered lower temperatures.—Unfed nymphs and adults were negatively geotactic which corresponds to their natural behaviour of climbing plants for catching hosts.—Adults of Amblyomma testudinis showed a higher rate of chemotaxis for snakes than for toads; substrate from snake cages containes chemotaxis inducing substances for more than 30 hours after elimination of the snakes.
  相似文献   
93.
94.
We use second harmonic generation (SHG) imaging to study and quantify a strong intrinsic SHG signal in skeletal muscle fiber preparations and single isolated myofibrils. The intrinsic signal follows the striation pattern of the muscle cells and is positioned at the sarcomeric location of the myosin filaments. Interestingly, the signal is enhanced at the region where the myosin heads are located on the myosin filaments. As the intrinsic signal reflects the subcellular structure in an accurate way, SHG can be used for noninvasive high resolution structural imaging without exogenous labels in living muscle cells. This may be very important for detecting changes in myofibrillar organization occurring under pathophysiological conditions, e.g., in cardiac and skeletal myopathies. Due to the strong dependency of SHG on orientation and symmetries of the tissue, it may allow the study of dynamic interactions between the contractile proteins actin and myosin during force production and muscle shortening. Furthermore, SHG imaging can be combined with other nonlinear microscopical techniques, such as laser scanning multiphoton fluorescence microscopy, to simultaneously measure other dynamic cellular processes, representing a complementary method and extending the range of nonlinear microscopical methods.  相似文献   
95.
Matrix metalloproteinase 13 (MMP-13), urokinase type plasminogen activator (uPA), and plasminogen activator inhibitor type-1 (PAI-1) have been reported to be involved in aseptic loosening of artificial hip joints. This study for the first time presents the protein levels of all of these factors in synovial-like interfaces between bone and prosthesis and in pseudocapsular tissues surrounding the artificial joint in patients with aseptic loosening (n=17) measured by ELISA. No differences were observed in the antigen expression of MMP-13, uPA, and PAI-1, comparing interface and pseudocapsular tissue. Also, no significant correlation between the protein expression of these factors and years from arthroplasty to revision or to type of fixation (cemented vs. cementless) was observed. As control, MMP-13, uPA, and PAI-1 antigen levels were also determined in the synovium of patients with osteoarthritis (n=10). Yet, the antigen levels of MMP-13, uPA, and PAI-1 in tissue specimens from patients with aseptic loosening of artificial hip joints were significantly higher compared to their expression in synovial capsular tissues obtained from patients with osteoarthritis. In conclusion, this study shows that elevated protein levels of uPA, PAI-1, and MMP-13 in periprosthetic pseudocapsular and interface tissues from patients after total hip replacement due to aseptic loosening seem not to be associated with the patient outcome.  相似文献   
96.
Consecutively admitted internal medical inpatients (N=294) who were psychiatrically assessed with the Schedules for Clinical Assessment in Neuropsychiatry in a two-phase design were followed up in a review of public files on their use of medical care over 18 months. Self-rated outcome was assessed from health and fitness ratings at admission and after 1 year. ICD-10 mental disorders had a statistically significant impact on the risk (odds ratio) of high use (above the 80th percentile) of primary care, as did ICD-10 anxiety/depression, and worry about illness (as assessed by the Whiteley-7 Scale). The authors found a less-than-significant tendency for mental illness to influence the use of inpatient admissions and self-rated outcome.  相似文献   
97.
The aim of the double-blind, placebo-controlled study was to investigate the effects of a continuous combined estrogen-progestogen treatment (Climodien, Lafamme) as compared with estrogen alone on vigilance in insomniac postmenopausal syndrome patients, objectified by EEG mapping. METHODS: In a 3-arm, 2-month parallel group design phase, patients received a combination of estradiol valerate 2 mg and the novel progestogen dienogest 3 mg (Climodien 2/3) or estradiol valerate 2 mg alone or placebo. In a subsequent open-label phase, all patients received estradiol valerate 2 mg+dienogest 2 mg (Climodien 2/2). EEG mapping was carried out before and after the 2-month double-blind phase as well as after the 2-month open-label treatment. RESULTS: As compared with placebo, Climodien 2/3 induced a marked and highly significant increase in absolute power in all frequency bands, specifically in alpha-2 activity. Moreover, a significant increase in relative alpha-2 power, a decrease in relative delta and beta power as well as an acceleration of the dominant frequency and of the delta and alpha centroids suggested a marked improvement in vigilance. In contrast, under estradiol valerate 2 mg alone, only a slight augmentation of alpha and attenuation of relative delta and beta power occurred, suggesting only a slight vigilance improvement as compared with placebo. Thus, dienogest 2 mg increased the estrogen effect, which was also confirmed by a statistical evaluation of the differences between Climodien 2/3 and estradiol valerate alone (augmentation of alpha-2, attenuation of relative beta, acceleration of the dominant frequency). Moreover, Climodien 2/2 also markedly increased alpha-2 power, decreased relative beta-2 power and accelerated the alpha centroid. Finally, comparing Climodien 2/3 with Climodien 2/2, there was even a dose-efficacy relation. CONCLUSIONS: Estradiol valerate 2 mg improves vigilance slightly, thereby confirming previous findings. The additional administration of dienogest does not minimize the effect of estrogen, but on the contrary increases it, which makes the combination superior to both placebo and estradiol valerate alone. Vigilance improvement may be of great therapeutic benefit to menopausal syndrome patients at a time when increased adaptability is needed to adjust to increasing sexual, marital, occupational and social difficulties known to occur specifically in this period of life.  相似文献   
98.
We employed the patch-clamp technique to investigate the effects of various phosphorylation pathways on activation and modulation of volume-activated Cl- currents (I Cl,vol) in cultured endothelial cells from bovine pulmonary arteries (CPAE cells). Half-maximal activation ofI Cl,vol occurred at a hypotonicity of 27.5 ± 1.2%. Run-down of the current upon repetitive activation was less than 15% within 60 min. Stimulation of protein kinase C (PKC) by phorbol-12-myristate-13-acetate (PMA) or by (–)-indolactam did not affectI Cl,vol. Down regulation of PKC activity by a 24-h preincubation of the cells with 0.2 mol/l PMA, or its inhibition by loading the cells with the specific inhibitory 19–31 pseudosubstrate peptide, did not influenceI Cl,vol. Trifluoperazine and tamoxifen fully blockedI cCl,vol with concentrations required for half-maximal inhibition of 3.0 and 2.4 mol/1 respectively. This inhibitory effect is probably not mediated by the calmodulin-antagonistic action of these compounds, because it occurs at free intracellular [Ca2+] of 50 nmol/l, which are below the threshold for calmodulin activation. The tyrosine kinase inhibitor herbimycin A (1 ol/1) and genistein (100 ol/1) did not affectI Cl,vol Exposing CPAE cells to lysophosphatidic acid (1mol/1), an activator of p42 MAPkinase and the focal adhesion kinase p125FAK in endothelial cells, neither evoked a Cl current nor affectedI Cl,vol Neither wortmannin (10 mol/1), an inhibitor of MAP kinases and of PI-3 kinase, nor rapamycin (0.1 mmol/1), which interferes with the p70S6 kinase pathway, affectedI Cl,vol Exposure of CPAE cells to heat or Na-arsenite, both activators of a recently discovered stress-activated tyrosine phosphorylation pathway, neither activated a current nor affected the hypotonic solution-induced Cl current. We conclude that none of the studied phosphorylation pathways is essential for the activation of the Cl current induced by hypotonicity.  相似文献   
99.
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号